I'm not aware of anyone having APFS booting 3,1 ... but this topic does interest me. I've also not seen anything newer than this for the 3,1: Boot ROM Version: MP31.006C.B05

Seeing the NVME addition being so simple it is now very tempting to me to go NVME instead of SATA3 add-in card to SSD which boots most of the time or the 4 slot mSATA add-in card which also boots most of the time, but have much slower r/w rates vs nvme.

I'd love to see native APFS+NVME booting from MP3,1. What else could we add here?